Volatile organic compounds (VOCs) and carbon monoxide (CO) in the air are contaminants and are harmful to human health. Methods have been developed to eliminate the contaminants.
Supported metal catalysts are found to be effective in low-temperature oxidation of CO and hydrocarbons and selective oxidation of propylene. (M. Haruta, Catal. Today 36: 153 (1997); M. T. Hayashi, K. Tanaka and M. Haruta, J. Catal 178: 566 (1998). ; M. Haruta and M. Date, Appl. Catal. A: Gen. 222: 427 (2001).)
Supported metal catalysts usually comprise nano-sized metal particles attached to a metal oxide support. One disadvantage of the supported metal catalysts is the low catalytic activity at low temperatures. Another disadvantage of the current supported metal catalysts is the short life of the catalyst as the metal atoms tend to sinter on the surface of the support, forming clusters of metals. Once the metal atoms are aggregated in clusters, their catalytic activity will be significantly reduced. In addition, the metal atoms are also susceptible to poisoning by halide- and sulfur-containing compounds.